1. Field of the Invention
The present invention relates to a zoom lens and an image pickup device. More particularly, the present invention relates to the technical field of a zoom lens suitable for an interchangeable lens mountable to a digital single-lens reflex camera, having high performance, and capable of providing sufficient back focus; and to the technical field of an image pickup device including the zoom lens.
2. Description of the Related Art
In recent years, in an image pickup device, such as a still camera or a video camera, pixelation of an image pickup element is being increased due to a rapid progress in digitization, so that there is an increasing demand for a zoom lens adaptable to an increase in performance. In addition, there is a high demand for reducing costs, weight, and size, in addition to increasing performance.
To meet such demands, in particular, in a zoom lens that covers a range from a wide-angle area to a medium-telephoto area, for example, an optical system having a two-lens group structure or an optical system having a four-lens group structure are proposed. In the optical system having a two-lens group structure, simplification of its mechanical structure and cost reductions are intended to be achieved. In the optical system having a four-lens group structure, higher performance is regarded as being important.
Optical systems having three-lens group structures for reducing weight and size are also proposed. Such optical systems include, for example, one including a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power in that order from an object side to an image side. (Refer to, for example, Japanese Unexamined Patent Application Publication No. 2002-72091 (Patent Document 1)).